One night in the early nineties, the playwright Kenneth Lonergan dreamed that he was at a friend’s apartment on the Upper West Side of Manhattan a decade or so earlier—though he wasn’t exactly himself. Rather, he was two characters simultaneously, composites of people he knew, both of them aimless but hyperverbal rich kids around nineteen or 20, one of whom was in the process of, he recalls, “playfully abusing” the other. The next morning, using the dream as a jumping-off point, Lonergan started to write. “I had never seen a play with just people that age in it,” he says. “And I definitely hadn’t seen one about my own background and group of friends, or that moment in our lives when we’d outgrown who we’d been in high school but were having a lot of difficulty figuring out who we were going to be next.”

The result was the foulmouthed and tenderhearted 1996 comedy This Is Our Youth, a beautifully observed portrait of privileged postadolescent paralysis in Reagan–era New York, rendered by a terrific young cast led by Mark Ruffalo. The play became an Off-Broadway smash and established Lonergan as a major new theatrical voice—and filled a future critic for this magazine with envy that he hadn’t written it himself. In the years since, it has been given productions all over the world and acquired an almost Catcher in the Rye–like cult status among both audiences and actors. Now, after a summer run at Chicago’s Steppenwolf Theatre, the play is coming to Broadway for the first time in a buzzy—and absolutely sensational—new production starring Michael Cera, Kieran Culkin, and Tavi Gevinson.

As in Lonergan’s dream, the action unfolds in an Upper West Side studio apartment belonging to Dennis (Culkin), a charismatic 21-year-old living large as a kind of bullying, dope-dealing Peter Pan. He’s visited by one of his lost boys, Warren (Cera), an impulsive nineteen-year-old geek toting a bag filled with vintage toys and $15,000 in cash stolen from his father after he was kicked out of the house. Soon, Dennis browbeats Warren into bankrolling an ill-conceived cocaine deal, and Warren finds himself in an awkward mating dance with Jessica (Gevinson), a smart, painfully self-conscious FIT freshman who he hopes will break his sexual cold streak. The play, though, is less concerned with plot-driven teen high jinks than with the way its disaffected characters struggle to negotiate the perilous transition to adulthood as the ground shifts beneath their feet.

Under the deft, sensitive direction of Anna D. Shapiro (August: Osage County; Of Mice and Men), the actors give nuanced, achingly real performances. As Dennis, Culkin stalks the stage with the ease of someone used to being the coolest kid in class, unaware that he’s already reached his sell-by date. Cera, playing a self-destructive cousin of the gawky adolescent he perfected in such films as Juno and Superbad, is all lurching movements and odd angles, one hand perpetually in his pants. Gevinson, a budding actress better known as an eerily precocious teenage fashion blogger turned avatar of girl power, is a revelation, allowing us to see the uncertainty and discomfort beneath her character’s poise and sophistication.

At 31, the boyishly handsome Culkin is the éminence grise and stage veteran of the group, not to mention the main reason they’re all here. “I played Warren in the London revival, and I felt like I hadn’t done it justice—at 20 I didn’t know what the show was even about,” he explains over an after-show drink in Chicago with his fellow cast members. “So I became obsessed with doing it again.” After turning down jobs in an attempt to make that happen, eventually Culkin decided that he wanted to play Dennis instead, and he gave a copy of the script to Cera while they were shooting Scott Pilgrim vs. The World. Cera, too, fell in love with the play and signed on to the enterprise, which led to a limited-run production in Sydney in 2012 that left both actors less than satisfied with their performances. “I had no idea what I was doing,” says Cera, who was making his professional stage debut.

Now, with Shapiro at the helm and Lonergan on hand to answer their questions, they’ve finally gotten it right—helped immeasurably by the luminous presence of Gevinson, whose final scene with Cera is a heartbreaker. “I don’t have as long and as intense a relationship with the play as these guys,” says Gevinson. “But I love how every moment is a microcosm of this bigger scary feeling that is so powerful when you’re young.”

“It’s a crucial moment for Dennis,” Culkin says. “He’s starting to lose control of this life that he built for himself. He peaked in high school, and he thinks that he’s just going to coast and that everyone is going to respect him forever. But you can’t grow up like that. People are becoming who they are and moving on.”

“Exactly,” says Cera, who’s 26. “At the end, Warren looks at Dennis and realizes, Oh, wait. I don’t have to be an appendage of your life. We have to be equals now, or else we can’t survive as adults in a friendship together. That’s the thing about any kind of relationship—it has to evolve and grow. It can’t get set in anything.”

Though the words youth and Broadway are not always comfortable partners, the presence of this magnetic young cast seems likely to change that a bit. Shapiro, meanwhile, hopes that the play itself will allow different generations to meet on common ground. “I don’t want grown-ups to look at it and go, ‘Oh, I remember that,’ ” she says. “And I don’t want young people to just think, Oh, even though they didn’t have iPhones then, that’s me. I want everyone to experience a connection to the struggle and pain we all go through at any moment of change in our lives—to make it feel like an eternal moment, not a nostalgic one.”

Still, there’s something poignant and fleeting about the specific turning point at which the kids of This Is Our Youth find themselves. For the eighteen-year-old Gevinson, this really is her youth—she graduated from high school in the middle of rehearsals. “It was probably a good time for me to bring out my Jessica because I was starting to feel like I was not whoever I had been for all of school,” Gevinson says. “And that’s equal parts exciting and terrifying: It’s that moment just before everything is about to explode—you’ve got your whole life ahead of you, but you’re just kind of grasping for these various identities to see how they fit, and you realize that you’re going to have to live with yourself for a long time.”